71 lines
1.0 KiB
Go
71 lines
1.0 KiB
Go
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package sike
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// Helpers
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// uint128 representation
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type uint128 struct {
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H, L uint64
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}
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func addc64(cin, a, b uint64) (ret, cout uint64) {
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ret = cin
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ret = ret + a
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if ret < a {
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cout = 1
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}
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ret = ret + b
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if ret < b {
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cout = 1
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}
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return
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}
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func subc64(bIn, a, b uint64) (ret, bOut uint64) {
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tmp := a - bIn
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if tmp > a {
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bOut = 1
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}
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ret = tmp - b
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if ret > tmp {
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bOut = 1
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}
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return
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}
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func mul64(a, b uint64) (res uint128) {
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var al, bl, ah, bh, albl, albh, ahbl, ahbh uint64
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var res1, res2, res3 uint64
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var carry, maskL, maskH, temp uint64
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maskL = (^maskL) >> 32
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maskH = ^maskL
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al = a & maskL
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ah = a >> 32
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bl = b & maskL
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bh = b >> 32
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albl = al * bl
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albh = al * bh
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ahbl = ah * bl
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ahbh = ah * bh
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res.L = albl & maskL
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res1 = albl >> 32
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res2 = ahbl & maskL
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res3 = albh & maskL
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temp = res1 + res2 + res3
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carry = temp >> 32
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res.L ^= temp << 32
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res1 = ahbl >> 32
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res2 = albh >> 32
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res3 = ahbh & maskL
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temp = res1 + res2 + res3 + carry
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res.H = temp & maskL
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carry = temp & maskH
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res.H ^= (ahbh & maskH) + carry
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return
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}
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